Elsevier

Physiology & Behavior

Volume 151, 1 November 2015, Pages 162-167
Physiology & Behavior

Positive human contact on the first day of life alters the piglet's behavioural response to humans and husbandry practices

https://doi.org/10.1016/j.physbeh.2015.06.030Get rights and content

Highlights

  • Positive human contact reduced duration of piglet’s escape behaviour to tail docking

  • Positive human contact reduced the pigs’ fear responses to humans

  • Positive human contact can alter the behavioural responses of piglets to stressors

Abstract

This experiment examined the effects of positive human contact at suckling on the first day of life on the behavioural and physiological responses of piglets to both humans and routine husbandry procedures. Forty litters from multiparous sows were randomly allocated to one of two treatments: Control (CC, minimal human interaction with day-old piglets) or Positive Contact (PC, human talking and caressing piglets during 6 suckling bouts on their first day of life, day 1). In each litter, 2 males and 2 females were randomly selected and their behavioural responses to tail docking (day 2), and to an experimenter (day 35) were studied. Escape behaviour at tail docking was assessed according to intensity (on a scale from 0 to 4 representing no movement to high intensity movement) and duration (on a scale from 0 to 3 representing no movement to continuous movement). At day 15 of age, a human approach and avoidance test was performed on focal piglets and at day 15, escape behaviour to capture before and after testing was recorded again. Blood samples for cortisol analysis were obtained from the focal piglets 30 min after tail docking and 1 h after weaning. Escape behaviour to tail docking of the PC piglets was of shorter duration than that of the CC piglets (P = 0.05). There was a tendency for the escape behaviour both before and after testing at day 15 to be of a lower intensity (P = 0.11 and P = 0.06, respectively) and a shorter duration (P = 0.06 and P = 0.08, respectively) in the PC piglets. There was a tendency for PC piglets to have higher cortisol concentrations after tail docking than the CC piglets (P = 0.07). Male piglets had higher cortisol concentrations after tail docking and after weaning than female piglets (P = 0.02 and P = 0.03). The results indicate that Positive Contact treatment reduced the duration of escape behaviour of piglets to tail docking. The role of classical conditioning, habituation and developmental changes in the observed effects of the Positive Contact treatment is unclear. Nonetheless, this experiment demonstrated that brief positive human contacts early in life can alter the behavioural responses of piglets to subsequent stressful events.

Introduction

Human–animal interactions are a critical feature of husbandry, which are often overlooked despite their importance to the welfare of the animal and the stockperson alike [1]. Intensive husbandry and housing practices affect the nature and amount of human contact that the animals receive [2] and routine negative interactions by stockpeople can result in animals becoming highly fearful of humans and, through stress, impaired welfare and productivity [1], [2], [3]. Adverse effects arising from negative emotional states, such as fear, on the welfare of animals are well-known. Many studies have found that negative handling by affecting fear of humans, may affect both the productivity and stress physiology of pigs [4], [5], [6], [7] and other farm animals [1], [2]. However, there is evidence that fear of humans can be reduced by improving the attitude and behaviour of the stockpeople to pigs [8], [9] and other farm animals [1], [2].

In comparison to fear responses in animals [1], identifying positive emotional experiences in animals arising from human interactions is less obvious [2], [10] and yet they may have powerful influences not only on the welfare of the animal but also on how the animal responds to aversive routine practices, such as painful or stressful procedures imposed by humans [1], [2]. Indeed, there are limited data indicating that positive emotional experiences in the presence of humans may ameliorate aversive situations for animals when in the presence of humans. For example, previous positive handling may improve ease of handling and reduce heart rates during loading of calves for transport [11], [12], reduce vocalisations in unfamiliar environments in the presence of humans [13], [14], reduce heart rate and salivary cortisol concentrations in lambs following tail docking [15], and reduce heart rates, kicking and restless behaviour in dairy cows during rectal palpation [16].

The increasing public concern about animal welfare has led to legislation in many countries aimed at reducing stressful or painful procedures. However, there are some aversive procedures that are at times necessary in livestock production, such as vaccination. In such situations the opportunities to utilise positive emotional responses to humans to minimize the magnitude of the stress response should be identified and explored.

Knowing that other mammals are likely to have emotional experiences (‘emotions’) that may resemble our own [10], the use of human contact in a conditioning process could influence future emotional experiences in animals to stressors when in the presence of humans. The concept of using conditioning, which can be defined as a form of learning in which the conditioned stimulus comes to signal the occurrence of another stimulus [17], to manipulate emotional responses of animals has been shown to have powerful effects on animal behaviour and physiology [1], [18], [19]. Indeed, Hemsworth et al. [20] observed that pigs fed in the presence of humans and positively handled were less fearful of humans, providing evidence of positive conditioning to humans through feeding. It has also been observed that positive handling involving gently patting or stroking pigs [21], [22], [23], and aversive handling and postural threats to pigs [23], [24] early in life may influence the pig's subsequent behavioural responses to humans. Also in poultry, handling very young chickens (1 day-old) reduced the birds' fear of humans [25].

We hypothesized that positive conditioning to humans during the first day of life will reduce the stress response of piglets to routine husbandry procedures performed by humans. Thus, the objective of the present experiment was to study the effects of providing piglets with the opportunity to associate humans with suckling on the first day of life on the behavioural and physiological responses of piglets to tail docking, ear tagging and oral and intramuscular vaccinations on the second day of life. Considering that situations of presumed positive emotional valence in mammals include gustatory pleasure during and after feeding [26] and knowing that the piglet's early life experiences may influence their subsequent stress response to humans or other social stimuli [22], [27], we also hypothesized that the presence of humans during suckling bouts is an effective method of positively conditioning piglets to humans, that is, reducing their fear of humans.

Section snippets

Animals, housing and management

All animal procedures were conducted with prior institutional ethical approval under the requirements of the NSW Prevention of Cruelty to Animals Act 1985, in accordance with the National Health and Medical Research Council/Commonwealth Scientific and Industrial Research Organization/Australian Animal Commission Code of Practice for the Care and Use of Animals for Scientific Purposes.

The experiment was conducted in a large commercial farm located in New South Wales, Australia. Sows (Large White ×

Results

On average, treatment imposition was conducted 6.7 ± 0.1 times (mean ± SE) on the PC litters. On average, each treatment imposition bout lasted 6.5 ± 0.7 min with 95.5 ± 7.8% of the piglets being present suckling or massaging at the udder.

Discussion

Few experiments have examined the effects of previous handling on the behavioural and physiological responses of animals to husbandry practices. In the present experiment, the Positive Contact treatment imposed on the first day of life reduced the behavioural response of piglets to tail docking at 2 days of age, with PC piglets showing a behavioural response to tail docking that was of shorter duration, but of similar intensity, to that of the CC piglets. Observations on the escape behaviour to

Acknowledgements

We thank Marianne Farish and Clara Singh for their help in conducting this experiment, and the staff from Rivalea Australia, especially Rebecca Morrison.

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